1. Field of the Invention
The invention relates in general to an electronic apparatus and protection apparatus thereof, and more particularly to an electronic apparatus, which uses a fuse to prevent a reverse current from inputting to a loading circuit therein via an adapter, and DC power input apparatus thereof.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional notebook computer structure. Referring to FIG. 1, the notebook computer 100 includes a loading circuit 110, a DC power input circuit 120, and a battery power device 130. The DC power input circuit 120 has a first switch 122, while the battery power device 130 has a second switch 132 and a battery 134. By switching the first switch 122 and the second switch 132, the notebook computer 100 can selectively use the DC power input circuit 120 to input a DC power DC1 to the loading circuit 110 via an adapter 140, or use the battery 134 to input a DC power DC2 to the loading circuit 110.
Owing that the first switch 122 and the second switch 132 usually have parasitic diodes 123 and 133 respectively, when a reverse voltage is inputted to the notebook computer 100 due to inverse-polarity connection of the adapter 140 or interior device damage, the induced reverse current Ir will still damage the loading circuit 110 or the battery 134 via the parasitic diode 123 or 133 even though the first switch 122 or the second switch 132 is turned off.
In order to prevent the reverse voltage from damaging the loading circuit 110 or the battery 134, a rectifier 124, such as a set of diodes 126 connected in parallel, is usually configured in the adapter 120 as a protection circuit. Through rectification effect of the rectifier 124, the above-mentioned reverse current Ir cannot flow by the diodes 126, thereby achieving the purpose of protecting the loading circuit 110 or the battery 134.
However, along with the increase of power used by the notebook computer 100, the bias current If inputted from the adapter 140 is getting larger and larger. Therefore, in order to effectively protect the loading circuit 110 or the battery 134, the above-mentioned rectifier 124 must have features of large bias current, low power consumption, and small reverse leakage current, which increases number of the diodes 126, thus magnify the space occupied by the rectifier 124, and largely increases the cost for manufacturing the notebook computer 100.